Detailed Study of Bandgap Energy Levels in CdTe Films Electrodeposited from Chlorine-Containing Solutions

Abstract

Thin films of CdTe are electrodeposited at different temperatures and potentials on stainless steel foil substrates from a 1M CdSO 4 solution containing chlorine (0.03 to 0.06 M). Current±voltage, conductivity±temperature and photoinduced current transient spectroscopy measurements have been performed on devices formed by evaporation of semitransparent Au electrodes on CdTe. The bandgap energy levels in these films have a distinctly different spectrum compared to films deposited from Cl-free solutions. In addition to some deep hole levels which can also exist in Cl-free films, a range of shallow hole traps (within 0.4 eV from the valence band edge) have been measured and their origins have been identified. The influence of these shallow hole traps on the charge transport mechanism and the activation energy of conductivity is discussed.

Characterization of space charge layer deep defects in n+-CdS/p-CdTe solar cells by temperature dependent capacitance spectroscopy

“…CdTe solar cells with Cu-evaporated back contacts demonstrated the capacitance peaks at a frequency of 100 kHz indicating the trap charge builds up due to deep levels. After incorporating the temperature dependence of cross-section in a) Email: prk6@njit.edu 0021-8979/2013/113(14)/144504/6/$30.00 V C 2013 AIP Publishing LLC 113, 144504-1 the activation energy, the observed deep levels were attributed to doubly ionized cadmium vacancies and Cu-related sites identical to reported experimental results 9,12,15,[20][21][22][23][24][25][26][27] obtained for deep defects. It is demonstrated that TDCS offers a rapid and convenient means of detecting and characterizing the properties of the deep centers.…”

“…Since the deep level associated with doubly charged cadmium vacancy was observed, it may be postulated that vacancy formation was suppressed, and the creation of interstitial favored in our devices. Rakhshani and Makdisi 25 have investigated the trap level with activation energy (0.88 eV) and r t $ 1.1 Â 10 À11 cm 2 in CdTe thin-film solar cells. In an earlier work, 9 we also observed this trap level.…”

Donor–acceptor pair photoluminescence spectra analysis in CdTe:Ag

“…5͑a͒ and 5͑b͔͒ work together; at the end, only the left-hand side process acts. An acceptor level at 0.090 eV above the valence band, owing to the Ag-V Cd 2Ϫ /Cl Te ϩ complex has been recently reported, 19 which supports the model proposed in Fig. 5.…”

Temperature Dependence of Electrical Characterization in n+ - CdS/ p - CdTe Thin Film Solar Cells – Study of Shallow/Deep Defects

“…Cadmium vacancies (V cd ) tend to form A -center with Cl donor leaving concentration of isolated V cd are low. In addition, this shallow trap levels seems to be associated with a hole trap as the activation energy of this defect was also observed by Photo induced current transient spectroscopic (PICTS) [15,16].…”

“…This further confirms the presence of this shallow trap level. In addition, it is clearly associated with hole trap, observed earlier by Photo induced current transient spectroscopic (PICTS) method [16,17].…”