CdTe is one of the most promising materials for thin-film solar cells. However, further improvement of its performance is hindered by its relatively short minority-carrier lifetime. Combining theoretical calculations and experimental measurements, we find that for both intrinsic CdTe and CdTe solar cell devices, longer minority-carrier lifetimes can be achieved under Cd-rich conditions, in contrast to the previous belief that Te-rich conditions are more beneficial. First-principles calculations suggest that the dominant recombination centers limiting the minority-carrier lifetime are the Te antisite and Te interstitial. Therefore, we propose that to optimize the solar cell performance, extrinsic p-type doping (e.g., N, P, or As substitution on Te sites) in CdTe under Cd-rich conditions should be a good approach to simultaneously increase both the minority-carrier lifetime and hole concentration.

We have fabricated 15.4%-and 12.4%-efficient CuIn 1-X Ga X Se 2 (CIGS)-based photovoltaic devices from solution-based electrodeposition (ED) and electroless-deposition (EL) precursors. Asdeposited precursors are Cu-rich CIGS. Additional In, Ga, and Se are added to the ED and EL precursor films by physical vapor deposition (PVD) to adjust the final film composition to CuIn 1-X Ga X Se 2 . The ED and EL device parameters are compared with those of a recent world record, an 18.8%-efficient PVD device. The tools used for comparison are current voltage, capacitance voltage, and spectral response characteristics.

The solution growth deposition of Bi~Se.~ (1), Bi2S3 (2), Sb2Se3 (8), a-PbO2 and T1203 (4), and Cul.sS and T1Se (5) thin films have been reported previously. The growth and photoelectrochemical solar cell based on electrodeposited CdSel-xTez thin films have also been reported (6-8). The deposition of CuInSe2 thin films by solution growth and also by the electropl.ating

The authors have fabricated 19.52% thin-film CuIn1−xGaxSe2 (CIGS)-based photovoltaic devices using single layer chemical bath deposited Cd1−xZnxS (CdZnS) buffer layer. The efficiency equals the world record for any thin-film solar cell and is achieved with reduced optical absorption in the window layer. Using current-voltage, quantum efficiency, and capacitance-voltage measurements, the CIGS/CdZnS device parameters are directly compared with those of CIGS/CdS devices fabricated with equivalent absorbers.

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