Crystallization Regulation and Morphological Evolution for HTM-free Tin-Lead (1.28eV) Alloyed Perovskite Solar Cells

There have been huge achievements of all-perovskite tandem solar cells,which recently realized the highest power conversion efficiency of 24.8%.However,the complex device structure and complicated manufacture processes severely restrict the further development of all-perovskite tandem solar cells.In this work,we successfully fabricated high-efficiency hole transport material-free(HTM-free)Sn−Pb alloyed narrow bandgap perovskite solar cells(PSCs)by introducing guanidinium thiocyanate(GASCN)and hydroiodic acid(HI)into the perovskite precursor solution.GASCN and HI play a positive synergy effect during perovskite crystallization process resulting in larger grain size,fewer surface defects,and lower trap density to suppress the Sn^(2+)oxidation degradation.Furthermore,they could effectively adjust the energy level of perovskite materials,reduce the energy level difference between perovskite and ITO resulting in more efficiently transport of free hole charge carriers.As a result,with adding GASCN and HI,the achieved highest power conversion efficiency of HTM-free devices increased from 12.58%to 17.85%,which is one of the highest PCEs among all values reported to date for the HTM-free narrow-bandgap(1.2-1.4 eV)Sn−Pb binary PSCs.Moreover,the optimized device shows improved environmental stability.Our additive strategy manifests a remarkable step towards the facile,cost-efficient fabrication of HTM-free perovskite-based tandem solar cells with both high efficiency and simple fabrication process.

Dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2-c][1,2,5]oxadiazole-based polymer donors with deep HOMO levels

Star nonfullerene acceptors like ITIC[1],IDIC[2],O-IDTBR[3],IT-4 F[4],COi8 DFIC[4],Y6[6]etc.continuously emerge and keep pushing the power conversion efficiency(PCE)of organic solar cells forward.These small molecules generally show narrow bandgaps,excellent visible to NIR light-harvesting capability,good electron mobility.

Improvement on the performance of perovskite solar cells by doctor-blade coating under ambient condition with hole-transporting material optimization

Numerous fabrication methods have been developed for high-efficiency perovskite solar cells(PSCs). However, these are limited to spin-coating processes in a glove box and are yet to be commercialized. Therefore, there is a need to develop a controllable and scalable deposition technique that can be carried out under ambient conditions. Even though the doctor-blade coating technique has been widely used to prepare PSCs, it is yet to be applied to high-efficiency PSCs under ambient conditions(RH ~45%, RT ~25 °C). In this study, we conducted blade-coating fabrication of modified high-efficiency PSCs under such conditions. We controlled the substrate temperature to ensure phase transition of perovskite and added dimethyl sulfoxide(DMSO) to the perovskite precursor solution to delay crystallization, which can facilitate the formation of uniform perovskite films by doctor-blade coating. The as-prepared perovskite films had large crystal domains measuring up to 100 μm. Solar cells prepared from these films exhibited a current density that was enhanced from 17.22 to 19.98 m A/cm^2 and an efficiency that was increased from 10.98% to 13.83%. However, the open-circuit voltage was only 0.908 V, probably due to issues with the hole-transporting layer. Subsequently, we replaced poly(3,4-ethylenedioxythiophene) polystyrene sulfonate(PEDOT:PSS) with Ni O x as the hole-transporting material and then prepared higher-quality perovskite films by blade-coating under ambient conditions. The as-prepared perovskite films were preferably orientated and had large crystal domains measuring up to 200 μm;The open-circuit voltage of the resulting PSCs was enhanced from 0.908 to 1.123 V, while the efficiency increased from 13.83% to 15.34%.

Structure influence of alkyl chains of thienothiophene-porphyrins on the performance of organic solar cells

Two new A-D-A porphyrin derivatives,denoted as XLP-I and XLP-II,were prepared through extending theπ-conjugation of thienothiophene-porphyrin center with phenylethynyl bridges and electron-deficient ethylrhodanine terminal units,and varying the structures of alkyl chain(linear vs branched)on peripheral thienothiophene substitutions of porphyrin rings.Both molecules show strong absorption in UV–visible–near-infrared region,good thermal stability,suitable energy levels,and ordered molecular packing in solid state.In organic solar cells,PC71BM was used as electron acceptor,and porphyrin small molecules were used as electron donors.The device based on XLP-I exhibits a power conversion efficiency(PCE)of 8.30%,an open circuit voltage(Voc)of 0.894 eV,and a fill factor(FF)of 62.1%.In contrast,the device based on XLP-II presents an inferior performance with a PCE of 3.14%,a Voc of 0.847 eV,and a FF of 49.3%.The better performance of XLP-I based device is mainly attributed to its optimized film morphology,excellent absorption,and well-balanced charge transport properties.

原位绿色反溶剂法钝化钙钛矿表界面缺陷提高钙钛矿太阳能电池效率和稳定性

目前钙钛矿太阳能电池多采用反溶剂成膜法制备钙钛矿吸收层,其优点是工艺简便、成本低廉.但是反溶剂法是一种快速结晶的制备方法,容易在钙钛矿薄膜晶粒的晶界和表面形成大量的缺陷,导致钙钛矿太阳能电池器件效率和稳定性的下降.虽然通过钙钛矿成膜之后再沉积钝化材料的后处理法可以钝化钙钛矿薄膜表面的缺陷,但是这种后处理法无法有效钝化晶粒界面处的缺陷.同时,由于目前多采用氯苯和甲苯等有毒溶剂作为反溶剂,制备过程产生的有毒污染较为严重.为了解决上述问题,本文将无毒的十六烷基三甲基氯化铵作为钝化剂直接加入无毒的异丙醇中作为绿色反溶剂,可以在钙钛矿晶体生长和成膜的过程中原位钝化晶粒的界面和表面的缺陷.通过这种原位钝化的方法,可以将钙钛矿太阳能电池器件的效率由20.3%提升至23.4%,并且稳定性也得到了明显提高.