Solar Energy Journal Subject Area Editor Prof Nicola Romeo passed away

It is with a heavy heart that we have to share the sad news of the passing of Prof Nicola Romeo (1940-2023), Solar Energy Journal Subject Area Editor for Photovoltaic Cells and Cell Physics.

Below, we share the obituary for Prof. Romeo by his son Alessandro. ISES extends our heartfelt condolences to the family of Prof Romeo. We are immensely grateful for Prof Romeo's work for Solar Energy Journal and solar energy overall. 


Obituary by Alessandro Romeo:

Prof. Nicola Romeo, Solar Energy Associate Editor, suddenly passed away on Wednesday 15th of November at the age of 83.

Nicola was an important member of the photovoltaics community, with a long-lasting career that started in the middle of the ‘60s of the last century. Graduating from the University of Messina in October 1965, he was appointed as a Full Professor in 1987 at the University of Parma.

Head of a research group since 1976, he has taught Physics at the Faculty of Science of the University of Parma since 1970. He was Director of the Parma Unit of the National Institute for the Physics of Matter (INFM) from 1988 to 1994. From 1986 to 1992, he was the principal investigator for the CNR-ENEA Energy Finalized Project Unit, “Thin Film Solar Cells of Compound Semiconductors ". Since 1984, he has been the local principal investigator of several international research projects funded by the European Commission (JOULE) on thin film solar cells. In the period between September 1980 to May 1981 he worked as a visiting professor at the Department of Material Science at Stanford University (USA).


In his early work at the end of the ‘60s and the early ’70s at the Universities of Messina, Bari, and Parma, his interests were already on the optical and electrical properties of binary materials such as ZnS [1] GaSe [2], In2Se3 [3] and GaS [4] [5], as well as on ternary compounds like ZnIn2S4 [6] and AgIn5S8 [7].

Since the early ‘70s, Prof. Nicola Romeo has been working on thin film photovoltaics being one of the world's early pioneers in this field. He introduced for the first time a CuGaSe2(CGS)/CdS solar cell obtaining an efficiency of 5% in 1977 [8], in the same year when also CuInSe2(CIS)/CdS was introduced. CuGaxIn1-xSe2 (CIGS) thin films on ZnSe single crystals were presented in 1979 [9], [10]. Also CdTe, as a photovoltaic material, was studied by Nicola in the early ’80s at the University of Parma and at Stanford University where he collaborated for 9 months with other PV-pioneers like Robert Bube and Alan Farhenbruch [11] [12].

Among his most important works, those concerning the discovery of two new methods, "Quasi-Rheotaxy" [13] and the C.G.T.F.C. (Concentration Gradient Thin Film Crystallization) process [14], should be mentioned. These processes allow the growth of thin layers of very high crystalline-quality materials. The first technique consists of depositing materials on thin metal layers kept at a temperature near to, but lower than their melting point. Quasi-rheotaxy was applied to prepare different semiconductor thin films for solar energy conversion, i.e. CdS, CdTe [15], Zn3P2, CuInSe2 [16], and CuGaSexTe1−x. where thin metal layers, such as Sn, Pb, Bi and Tl deposited on stainless steel or sapphire, have been used as substrates.

Between the ‘80s and ‘90s, Prof. Romeo concentrated his work on electroluminescent compounds and the preparation and study of CIS, CIGS, and CdTe solar cells. He applied innovative processes like the low resistivity CdS by sputtering in Ar-H2 atmosphere [17] or the CdTe doping by nitrogen incorporation in a Cd-Te co-evaporation process [18]. By introducing alternative deposition techniques such as flash evaporation and RF-sputtering for CIGS and CdTe, he reached remarkable results like the highest substrate configuration CdTe efficiency for those times (9.16%) [19].

Innovation was one of the highest peculiarities in his works in every decade of his research history, in the late ‘90s Nicola introduced a new stable back contact based on Sb2Te3, at those times the high instability of CdTe devices by Cu application in the back contact was a very big issue. With the introduction of Sb2Te3, the device stability reached unknown values since then, with a remarkable efficiency of 14.6% (the world record efficiency was 15.8%) [20]. This was so promising to be adopted by Antec Gmbh, one of the world’s first CdTe production lines, based on the research work of Dieter Bonnet, a pioneer and a close friend of Nicola and with whom he shared several European research projects in the JOULE program.

In the early 2000s, the importance of CdTe chlorination stimulated Nicola to introduce an HCF2Cl treatment replacing CdCl2 for a simple and non-toxic CdTe recrystallization treatment [21]. This together with a new As2Te3:Cu back contact and an engineered RF-sputtered CdS allowed the construction of an innovative pilot production plant (15 MW/y) in Lonate, Italy (see Figure 2), where Nicola was a consultant [22]. In his career, he has published more than 150 works on CdTe/CdS and CuInGaSe2/CdS thin film solar cells.

One of his peculiarities was that, despite his responsibilities as a full professor and head of the laboratory, he was always very active in the lab and he was preparing his samples, which is something rarer and rarer nowadays.


As a son, after his passing, I have personally received several different memories from his national and international colleagues and friends. All of them shared some things in common: the capability of inspiring in every day of his work, his willingness to spread his knowledge to young enthusiasts, and his attitude to help other people reach the desired results. In a word: he was a generous man with high values.

His love for research was such that he influenced a large number of students who are still working in this fascinating field, as well as me and my sister so that now both of us are passionate researchers, even if in different fields.



[1] A. Cingolani, A. Levialdi, and N. Romeo, “ZnS photo- and electro-luminescence compared at different electric-field strengths,” Il Nuovo Cimento B Series 10, vol. 51, no. 1, pp. 210–212, 1967, doi: 10.1007/BF02712336.

[2]         N. Romeo, “Experimental Evidence for the Validity of Lampert’s Theory in the Negative Resistance Region of the GaSe(Sn),” physica status solidi (b), vol. 34, no. 2, pp. 717–720, 1969, doi:

[3]         N. Romeo, “Negative magnetoresistance in In2Se3 single crystals,” physica status solidi (a), vol. 26, no. 2, pp. K187–K190, 1974, doi:

[4]         N. Romeo, “Negative Resistance in GaS Single Crystals,” physica status solidi (b), vol. 36, no. 1, pp. 153–156, 1969, doi:

[5]         N. Romeo, “Memory switching in GaSe, GaS, and GaS<inf>x</inf>Se<inf>(1-x</inf>) (0&lt;x&lt;1) single crystals,” J Appl Phys, vol. 42, no. 9, pp. 3643–3644, 1971, doi: 10.1063/1.1660784.

[6]         S. Mora, C. Paorici, and N. Romeo, “Properties of the Ternary Compound ZnIn2S4 at High Electric Field,” J Appl Phys, vol. 42, no. 5, pp. 2061–2064, Dec. 2003, doi: 10.1063/1.1660487.

[7]         C. Paorici, L. Zanotti, N. Romeo, G. Sberveglieri, and L. Tarricone, “Crystal growth and properties of the AgIn5S8 compound,” Mater Res Bull, vol. 12, no. 12, pp. 1207–1211, 1977, doi:

[8]         N. Romeo, G. Sberveglieri, L. Tarricone, and C. Paorici, “Preparation and characteristics of CuGaSe<inf>2</inf>/CdS solar cells,” Appl Phys Lett, vol. 30, no. 2, pp. 108–110, 1977, doi: 10.1063/1.89307.

[9]         C. Paorici, L. Zanotti, N. Romeo, G. Sberveglieri, and L. Tarricone, “Crystal growth and properties of CuGaxIn1−xSe2 chalcopyrite compound,” Solar Energy Materials, vol. 1, no. 1, pp. 3–9, 1979, doi:

[10]       A. Nur Salad, N. Romeo, G. Sberveglieri, O. Vigil, and L. Zanotti, “Growth and characterization of CuGaxIn1−xSe2 thin films for solar cells,” Materials Chemistry, vol. 4, no. 3, pp. 549–555, Sep. 1979, doi: 10.1016/0390-6035(79)90040-3.

[11]       N. Romeo, S. Tosi, and S. Azzi, “Low resistivity n-type CdTe thin films doped with lead,” Thin Solid Films, vol. 82, no. 1, pp. L121–L123, 1981, doi:

[12]       N. Romeo and R. H. Bube, “Large grain CdTe thin films on Sb–Bi alloy‐coated Ta substrates,” Journal of Vacuum Science and Technology, vol. 21, no. 4, pp. 969–971, Nov. 1982, doi: 10.1116/1.571876.

[13]       N. Romeo, “Quasi-Rheotaxy: Growth of large crystalline grain thin films on quasi-liquid substrates,” J Cryst Growth, vol. 52, no. PART 2, pp. 692–698, Apr. 1981, doi: 10.1016/0022-0248(81)90364-X.

[14]       N. Romeo, “A simple new method to grow crystalline metallic thin films on amorphous substrates,” J Appl Phys, vol. 64, no. 9, pp. 4762–4764, 1988, doi: 10.1063/1.341193.

[15]       N. Romeo, V. Canevari, G. Sberveglieri, A. Tosi, and G. Celotti, “Large-grained (111)-oriented CdTe thin films grown by ‘quasi-rheotaxy’ on steel substrates,” Thin Solid Films, vol. 90, no. 4, pp. 413–417, 1982, doi:

[16]       L. P. Bicelli, G. Razzini, N. Romeo, and V. Canevari, “Photoelectrochemical characterization of n-CuInSe<inf>2</inf> films prepared by quasi-rheotaxy,” Surface Technology, vol. 25, no. 4, pp. 327–334, 1985, doi: 10.1016/0376-4583(85)90084-6.

[17]       N. Romeo, A. Bosio, V. Canevari, and D. Seuret, “Low resistivity CdS thin films grown by r.f. sputtering in an Ar-H2 atmosphere,” Solar Cells, vol. 22, no. 1, pp. 23–27, 1987, doi:

[18]       N. Romeo, A. Bosio, V. Canevari, C. Spaggiari, and L. Zini, “P-type CdTe thin films doped during growth by neutral high energy nitrogen atoms,” Solar Cells, vol. 26, no. 3, pp. 189–195, 1989, doi:

[19]       N. Romeo, A. Bosio, and V. Canevari, “Large Crystalline Grain Cdte Thin Films for Photovoltaic Application,” International Journal of Solar Energy, vol. 12, no. 1–4, pp. 183–186, 1992, doi: 10.1080/01425919208909761.

[20]       N. Romeo, A. Bosio, R. Tedeschi, A. Romeo, and V. Canevari, “Highly efficient and stable CdTe/CdS thin film solar cell,” Solar Energy Materials and Solar Cells, vol. 58, no. 2, pp. 209–218, 1999, doi: 10.1016/S0927-0248(98)00204-9.

[21]       S. Mazzamuto, L. Vaillant, A. Bosio, N. Romeo, N. Armani, and G. Salviati, “A study of the CdTe treatment with a Freon gas such as CHF2Cl,” Thin Solid Films, vol. 516, no. 20, pp. 7079–7083, 2008, doi:

[22]       N. Romeo, A. Bosio, and A. Romeo, “An innovative process suitable to produce high-efficiency CdTe/CdS thin-film modules,” SOLAR ENERGY MATERIALS AND SOLAR CELLS, vol. 94, pp. 2–7, 2010, [Online]. Available:


Nicola Romeo in his office in 2006.