Determination of the minority carrier diffusion length in compositionally graded Cu(In,Ga)Se2 solar cells using electron beam induced current

A method is proposed and tested which allows for the accurate determination of the carrier collection efficiency and minority carrier diffusion length in Cu(In,Ga)Se2 solar cells using energy dependent electron beam induced current. Gallium composition gradients across the film thickness introduce quasielectric fields that are found to improve collection efficiency when they are located toward the rear of the sample. The quasielectric fields are also shown to reduce the influence of back surface recombination. The strengths and limitations of this technique are discussed and compared with external quantum efficiency measurements.

[1]  A. Forchel,et al.  Minority-carrier lifetime and efficiency of Cu(In,Ga)Se2 solar cells , 1998 .

[2]  C. Donolato.  A reciprocity theorem for charge collection , 1985 .

[3]  R. Scheer,et al.  Determination of charge carrier collecting regions in chalcopyrite heterojunction solar cells by electron-beam-induced current measurements , 1997 .

[4]  R. Scheer,et al.  Depth dependent collection functions in thin film chalcopyrite solar cells , 1995 .

[5]  M. Green.  Do built‐in fields improve solar cell performance? , 2009 .

[6]  M. Ferenets,et al.  Thin Solid Films , 2010 .

[7]  R. Annan.  Photovoltaics. , 1985, Science.

[8]  V. Bermudez,et al.  Evaluation of diffusion-recombination parameters in electrodeposited CuIn(S, Se)2 solar cells by means of electron beam induced current experiments and modelling , 2009 .

[9]  Rommel Noufi,et al.  Recombination kinetics and stability in polycrystalline Cu(In,Ga)Se2 solar cells , 2009 .

[10]  Carrier collection in Cu(In,Ga)Se2 solar cells with graded band gaps and transparent ZnO:Al back contacts , 2007 .

[11]  B. von Roedern,et al.  Comparison of device performance and measured transport parameters in widely‐varying Cu(In,Ga) (Se,S) solar cells , 2006 .

[12]  Rommel Noufi,et al.  Properties of 19.2% efficiency ZnO/CdS/CuInGaSe2 thin‐film solar cells , 2003 .

[13]  D. B. Wittry,et al.  Investigation of minority‐carrier diffusion lengths by electron bombardment of Schottky barriers , 1978 .

[14]  R. Scheer.  Simulation of electron-beam-induced-current profiles for thin-film heteroj unction analysis , 1995 .

[15]  Su-Huai Wei,et al.  Band offsets and optical bowings of chalcopyrites and Zn‐based II‐VI alloys , 1995 .

[16]  I. Repins,et al.  Long lifetimes in high-efficiency Cu(In,Ga)Se2 solar cells , 2008 .

[17]  I. Repins,et al.  19·9%‐efficient ZnO/CdS/CuInGaSe2 solar cell with 81·2% fill factor , 2008 .