Temperature dependent electrical characterization of thin film Cu₂ZnSnSe₄solar cells

Abstract

Impedance spectroscopy (IS) and current-voltage characteristics measurements were applied to study properties of a Cu 2 ZnSnSe 4 (CZTSe) thin film solar cell. IS measurements were done in the frequency range 20 Hz to 10 MHz. The measurement temperature was varied from 10 K to 325 K with a step ∆T = 5 K. Temperature dependence of V oc revealed an activation energy of 962 meV, which is in the vicinity of the band gap energy of CZTSe and hence the dominating recombination mechanism in this solar cell is bulk recombination. Different temperature ranges, where electrical properties change, were found. Interface states at grain boundaries with different properties were revealed to play an important role in impedance measurements. These states can be described by introducing a constant phase element in the equivalent circuit.

Revealing the beneficial effects of Ge doping on Cu2ZnSnSe4 thin film solar cells

“…For the 0 nm Ge devices it increases to 14 meV, and for the 50 nm Ge device two regions have to be distinguished. For the first temperature range of 300-150 K an activation energy of 23 meV was found which increases to 48 meV for temperatures <130 K.Similar observations of two thermally activated processes are reported in literature, where the first activation energy is related to grain boundaries or shallow acceptor like defects and the second one at lower temperature to different processes like carrier localization in potential wells, radiative recombination or Mott's variable range hopping where holes occupy shallow states in the band gap and if a sufficient high concentration of this states is present the overlapping of their wave functions could form an impurity band [43],[45]. Since the high temperature activation energy is the lowest for the 10 nm Ge device an reduction of grain boundary barrier height for the optimal Ge doping range of 10 nm could be speculated because in this temperature range thermionic emission across grain boundaries is typically the dominant conduction mechanism [46].…”

“…, where E a is the activation energy. [43] In earlier studies this exponential increase in series resistance was related to an non-ohmic back contact of Kesterite and MoS(e) 2 /Mo interface [5] however it is more likely that bulk conductivity itself limits the series resistance. Besides dark JV-T analysis, the illuminated curves were recorded as well and device parameters extracted, In Figure 5 the J sc , efficiency (eff) as well as V oc for different temperatures is shown.…”

A study of S doped ZnSb

“…That Zn vacancies yield p-type behavior has commonly been argued and has also been put into a theoretical framework [16,33]. Regarding clusters acting as neutral centers, there are several examples of that with other semiconductors, one common case is As in Si [30,34,35], another is the V Cu +Zn Cu complex in the photovoltaic material Cu 2 ZnSnS 4 (CZTS) [36]. We can tentatively forward a simple hypothesis, which would explain parts of the results and lack of n-type behavior.…”

Comparing the Effect of Mn Substitution in Sulfide and Sulfoselenide‐Based Kesterite Solar Cells

“…The values for sulfide films are significantly lower than their respective bandgap in comparison with sulfoselenide. As the activation energy is less than the bandgap ( E A < E g ), this suggests that the interface recombination is the dominant recombination mechanism . The double‐layer structure increase the E A , which indicates reduction in interfacial barrier height that eases the charge transport through the junction .…”

“…As the activation energy is less than the bandgap (E A < E g ), this suggests that the interface recombination is the dominant recombination mechanism. [17] The double-layer structure increase the E A , which indicates reduction in interfacial barrier height that eases the charge transport through the junction. [18] Meanwhile, for sulfoselenide films, the activation energy is closer to bandgap (E A % E g ), which suggests space charge recombination.…”