Enhancement of open-circuit voltage and the fill factor in CdTe nanocrystal solar cells by using interface materials

Abstract

Interface states influence the operation of nanocrystal (NC) solar cell carrier transport, recombination and energetic mechanisms. In a typical CdTe NC solar cell with a normal structure of a ITO/p-CdTe NCs/n-acceptor (or without)/Al configuration, the contact between the ITO and CdTe is a non-ohm contact due to a different work function (for an ITO, the value is ~4.7 eV, while for CdTe NCs, the value is ~5.3 eV), which results in an energetic barrier at the ITO/CdTe interface and decreases the performance of the NC solar cells. This work investigates how interface materials (including Au, MoO(x) and C₆₀) affect the performance of NC solar cells. It is found that devices with interface materials have shown higher V(oc) than those without interface materials. For the case in which we used Au as an interface, we obtained a high open-circuit voltage of 0.65 V, coupled with a high fill factor (62%); this resulted in a higher energy conversion efficiency (ECE) of 5.3%, which showed a 30% increase in the ECE compared with those without the interlayer. The capacitance measurements indicate that the increased V(oc) in the case in which Au was used as the interface is likely due to good ohm contact between the Au's and the CdTe NCs' thin film, which decreases the energetic barrier at the ITO/CdTe interface.

Solution processed CdTe/CdSe nanocrystal solar cells with more than 5.5% efficiency by using an inverted device structure

“…33 This value is 40% higher than those of conventional CdTe-CdSe NC solar cells (ref. When we select R s  A = 5.0 O, R sh  A = 5.0  10 6 O, n = 1.45, kT = 0.026 eV, we find that the J-V curve simulated (solid line) from the above formula conforms to our experimental data (open circles) well.…”

Solution-Processed Efficient Nanocrystal Solar Cells Based on CdTe and CdS Nanocrystals

“…With the progress of nanomaterials fabrication techniques, various high quality semiconductor NCs have been synthesized and investigated. However, only a few of these materials such as PbS [7,8], PbSe [9], CdTe [10][11][12], and CuInSe 2 (CIS) [13,14], have been successfully exploited for photovoltaic application. Among these materials, CdTe may be one of the most studied NCs due to their reasonable At an optimized heat treatment temperature of 380 • C, we obtained the best device, with V oc = 0.56 V, J sc = 17.26 mA/cm 2 , FF = 52.84%, and PCE = 5.14%.…”

CdTe Nanocrystal Hetero-Junction Solar Cells with High Open Circuit Voltage Based on Sb-doped TiO2 Electron Acceptor Materials

“…Compared to PbS NC, CdTe NC is less complex and more stable in air, which permits devices to be fabricated under ambient conditions. Thus, CdTe NC thin film has been studied intensively [14,15,16,17,18,19,20]. The working principle of efficient CdTe NC solar cells is based on the p-n heterojunction that contains two media: an electron donor and electron acceptor.…”