Earth-abundant Cu-based chalcogenide semiconductors as photovoltaic absorbers

摘要

The materials Cu3PQ4 (Q = S, Se) of the enargite structure are studied as photovoltaic (PV) absorbers. Optical band gaps in the series Cu3PS_(4-x)Se_x (0≤x ≤ 4) are found to range from 2,36 eV (x = 0) to 1.35 eV (x = 4). Seebeck measurements on powder samples at room temperature yield large positive values (>100 μV K~(-1)) indicating p-type behavior. Hole carrier concentrations are found in the range of 10~(16)-10~(17) cm~(-3). Crystal structures of Cu3PS_(1.89)Se_(2.11) and Cu3PS_(0.71)Se_(3.29) are refined in the orthorhombic space group Pmn2, with the unit-cell parameters - Cu3PS_(1.89)Se_(2.11): a = 7.5034(5) A, b = 6.4951(5) A, c = 6.2174(4) A, and Cu3PS_(0.71)Se_(3.29): a = 7.6164(6) A, b = 6.5945(6) A, c = 6.3107(5) A. Photoelectrodes, fabricated from Cu3PSe4 single crystals, exhibit p-type photoresponse and yield open circuit voltages V_(oc) = 0.12 V and short circuit currents J_(sc) = 0.25 mA cm~(-2) under 100 mW cm~(-2) of 660 nm illumination in a non-aqueous cobaltocene/cobaltocenium cell.