The Preparation Of Transition Metal Chalcogenides And Its Application In Solar Cells

The prosperity of human society largely depends on the supply of energy and fossil fuel has always been the most reliable energy source of mankind.However,as a non-renewable energy source,it is inevitable that fossil fuels will run out oneday.As a result,renewable energy,especially solar energy,arouses worldwide attention.The third generation of photovoltaic cells is the one that solar energy can be directly converted into electricity by using solar cell,which represents the forefront of solar energy technology with high power conversion efficiency and low production cost.Dye-sensitized solar cell（DSSC）and perovskite solar cell（PSC）are promising energy conversion devices among the third generation.However,many aspects need to be addressed before they are available as commercial products.Counter electrode is a key component of DSSC and an effective counter electrode must have high conductivity and good catalytic activity.Currently,the most commonly used counter electrode is Pt,which impose restrictions on the commercialization of DSSC.For PSC,its photoelectric performance largely depends on carrier transport material and the widely used electron transport material is TiO₂.Usually,it requires high temperature calcination process to get ideal transport performance,which restricts its application on flexible substrate.Therefore,this paper focuses on the improvement of counter electrode materials of DSSC and electron transport materials of PSC.The main research contents of this paper are summarized as follows:（1）Co_0.85Se nanopetals were synthesized by solvent thermal method and used as counter electrode materials of DSSC.The DSSC based on optimized Co_0.85Se nanopetal counter electrode achieves a power conversion efficiency of 8.00%which is superior to that of the DSSC assembled with conventional sputtered Pt counter electrode（7.83%）.（2）CoSe₂ nanorods were synthesized by solvent thermal method and used as counter electrode materials of DSSC.The DSSC devices assembled with optimized CoSe₂ nanorod,Pt counter electrode obtain power conversion efficiency of 8.38%and 7.83%,respectively.（3）Transparent Ni_0.85Se and semi-transparent Ni_0.85Se/rGO composite counterelectrodes were prepareded by hydrothermal and spin-coating process.The DSSC devices based on optimized Ni_0.85Se,Ni_0.85Se/rGO and conventional sputtered Pt counter electrode obtain power conversion efficiency of 8.96%,9.75%and 8.15%,respectively.Moreover,when adding a mirror under Ni0.85Se counter electrode,the power conversion efficiency is further improved to 10.76%.（4）Transparent CoSeO₃·2H₂O and semi-transparent CoSeO₃·2H₂O/rGOcomposite counter electrodes were prepareded by hydrothermal and spin-coating process.The power conversion efficiency of DSSCs based on optimized CoSeO₃·2H₂O,CoSeO₃·2H₂O/rGO and conventional sputtered Pt counter electrode is 8.90%,9.89%and 8.39%,respectively.Besides,when putting a mirror under CoSeO₃·2H₂O counter electrode,the power conversion efficiency can be further improved to 11.04%.（5）Re-dispersible CdS nanoparticles were synthesized by solvent thermal methodand CdS films were prepared on FTO by spin-coating CdS solution of toluene without annealing or heat treatment process.The as-prepared CdS films were used as electron transport layer of PSC.The PSC device based on optimized CdS electron transport layer reaches a power conversion efficiency of 16.50%under reverse scan.（6）Cr₂O₃ nanosheets were synthesized by solvent thermal method.The as-prepared Cr₂O₃ nanosheets can be re-dispersed in toluene to form uniform solution so that Cr₂O₃ film on FTO can be prepared by spin-coating method without annealing or heat treatment process.The as-obtained Cr₂O₃ films were used as electron transport layer of PSC.The best-performed PSC device with Cr₂O₃-6000electron transport layer yields a power conversion efficiency of 16.23%,while the best-performed PSC with high temperature calcining TiO₂ electron transport layer achieves a power conversion efficiency of 17.04%.