Photoluminescence investigation of Cu 2 ZnSnS 4 thin film solar cells

Abstract

Cu 2 ZnSnS 4 (CZTS) is a promising absorber for thin film solar cells which is non-toxic and consists of only abundant elements. In order to achieve higher solar cell efficiencies for this material, a better understanding about its defect structure is necessary. In this paper photoluminescence (PL) from sputtered CZTS thin film solar cells which differ in buffer layer thickness was studied. In the PL spectra three broad peaks could be distinguished between 0.9 and 1.3 eV. The PL measurements as a function of temperature and excitation power density revealed the presence of potential fluctuations. The separations between the band edge of the photoluminescence excitation signal and the PL emission peaks are large, which indicates that PL involves trapping of carriers by deep -level defects.

Limitation factors for the performance of kesterite Cu2ZnSnS4thin film solar cells studied by defect characterization

“…As shown in Fig. 3(c), a large blue shi of peak energy ($25 meV) with slope of 14.3 meV per decade is observed when excitation density is increased, which is consistent with previous observations 21, [25][26][27][28] in solar cell with large potential uctuations. Actually, the large blue shi with the increasing laser power is one feature of donor-acceptor pair (DAP) transition or band to tail (BT) transition.…”

Synthesis, theoretical and experimental characterisation of thin film Cu2Sn1-Ge S3 ternary alloys (x = 0 to 1): Homogeneous intermixing of Sn and Ge

“…Returning to the question if SnS is really present in the film with x ¼ 0.63, a photoluminescence peak around 1.3 eV [49] due to its band-to-band transition might be observable. However, for this sample it would likely overlap with the band-to-band transition from the CTGS itself.…”

Wild band edges: The role of bandgap grading and band-edge fluctuations in high-efficiency chalcogenide devices

“…Thus, it should be expected that CZTS exhibits a larger tendency toward disorder, band tails, and band-edge fluctuations. A number of studies have observed such effects (for example, [20], [41], [42]). A comparison of NREL CIGS and Cu 2 ZnSnSe 4 (CZTSe) by constant final state yield spectroscopy indicates that the concentration of near-bandedge states is three to five times higher for CZTSe than for CIGS [46].…”