Study On The Controllable Preparation And Mechanism Of The Functional Layer Of Inverted Planar Heterojunction Solar Cell

In recent years,organic-inorganic halide perovskite solar cells?PSCs?have achieved tremendous developments due to their versatile characteristics,such as low cost,large-scale and flexible fabrication and high efficiency,whereas the power conversion efficiencies?PCEs?can exceed 22%.This rapid increase in PCEs is the result of the continuous efforts in improving the quality of perovskite films and optimization of the device structures.In this thesis,we used the inverted p-i-n planar-heterojunction structure as the model to study the growth of perovskite films and preparation process of hole-and electron-transport layers.Accordingly,we hope to control the functional layers and improve photovoltaic performance facilely.The main contents in this thesis are as follows:1.To improve the preparation technology of MAPb I3 film in air: We have systematically studied the growth of perovskite films by optimizing relative parameters during DMSO-vapor annealing,including the vapor concentration and the annealing time.If we want to obtain excellent perovskite films with smooth,compact,pinhole free and large crystal,it is necessary to use DMSO concentration of about 1.5 mg/ cm3 and at least 20 minutes for the following thermal annealing as the processing parameters to reconstruct perovskite crystal at the initial stage of crystal growth,leading to the PCEs increasing from 11.9% to 15.7%.In addition,we also studied the crystallization mechanism of perovskite films,and confirmed that the solvent atmosphere would destroy the surface of the films.Therefore,we proposed that if we would like to acquire the high-quality perovskite films,it is beneficial for annealing treatment without solvent at the end of crystallization.2.To explore preparation technology and study mechanism for the hole transport layer of poly-TPD.Due to the low conductivity and sensitivity of the device to the thickness of the poly-TPD,we studied the effect of poly-TPD concentration on the device performance.It is found that the poly-TPD films prepared by the published methods have poor flatness and repeatability.In this paper,the poly-TPD film was deposited on the hot substrate,because the increase of the substrate surface energy can greatly improve the quality of poly-TPD film,and enhance the effective coverage rate of poly-TPD film,and significantly improve the flatness of the film.Therefore,the PCE is increased from 14.87% to 18.60%,and the repeatability of device performance is greatly improved.3.To improve the preparation process of the electron-transport layer PC₆₁ BM.We also used the hot substrate preparation technology to deposit the electron transport layer PC₆₁ BM,which could solve the problem of poor adhesion and low film coverage of PC₆₁ BM layer.When the substrate temperature is controlled at 60?,we can obtain the uniform and pinhole-free surface morphology of perovskite layer,leading to the highest PCE of 19.16%.The high quality of electron transport layer can effectively reduce the surface defects of the perovskite film and inhibit the recombination of the carriers at the interface between the perovskite and electrode.Hence,it is dramatically beneficial for improving the charge carrier extraction and transport.