Ex situ bismuth doping for efficient CdSeTe thin-film solar cells with open-circuit voltages exceeding 900 mV

摘要: The focus of CdSeTe thin-film solar cell doping has transitioned from copper (Cu) doping to group V doping. In situ group V doping has resulted in a new record power conversion efficiency (PCE) of 23.1%, with open-circuit voltages (VOCs) exceeding the 900 mV mark. Here, we report that ex situ bismuth (Bi)-doped CdSeTe thin-film solar cells show VOCs exceeding 900 mV and a champion PCE of 20.6%. Characterizations revealed that the Se-rich CdSeTe region near the front junction promotes Bi ions to occupy the anion sites and dope this region weakly p-type. Bi ions in the CdTe-dominating back surface region occupy the cation sites and are oxidized. This ex situ Bi doping with BiF3 as a dopant precursor offers several advantages, including simplicity, high tolerance to the processing environment, and no requirement of additional Cd vapor or special activation processes, making it highly adaptable for …