Interface Engineering Of Organic/Inorganic Hybrid Solar Cells

This thesis was based on the silicon (Si)-conjugated polymer hybrid solar cells. Inthis thesis, the device performance influenced by the morphology and passivation ofsilicon substrates surfaces were investigated. The device with high performance andstability was fabricated by controling the interface of Si/polymer. Si nanowire arrays(SiNWs) were fabricated by metal-assisted chemical etching method, and their densitieswere tuned through slowly chemical etching. The surface density of trap states and thevelocity of surface carrier recombination were dramatically reduced utilizing a two-stepmethod of chloridization/alkylation. High efficiency of over10%and stableorganic/inorganic hybrid photovoltaic devices were fabricated based on the densitycontrollable, organic monolayer surface passivated SiNWs and poly(3-hexylthiophene)(P3HT) or poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)(PEDOT:PSS).Scanning electron microscope (SEM), transmission electron microscope (TEM),UV-Vis spectrophotometer (UV-Vis), X-ray photoelectron spectroscopy (XPS), transientphotovoltage (photocurrent) decay were used to analyse the interface engineeringsystematically. The results indicated that the surface morphology and passivation playimportant roles on device performance because they dominate the charge recombinationprocess. My works maily consist of following parts:1. Preparation of SiNWs with regular structure by metal-assisted chemical etchingmethod to fabricate. The controllable surface morphology of SiNWs was achievedthrough a simple and efficient chemical etching method. The controllable surface energydiagram, the density of trap states, charge recombination velocity and chemical stabilitywere achieved through the surface passivation.2. Fabrication of Si/P3HT hybrid photovoltaic devices with different surfacemorphology and passivation layer. The device performance was characterized bycurrenet-volatage (J-V) and external quantum efficiency (EQE), and the interfacemorphology were measured by SEM, TEM, and UV-Vis. The results indicated thatdevice performance could be enhanced by optimizing the surface morphology and passivaiton of Si substrates.3. Fabrication of devices with the structure of heterojuction with organic thinlayer were fabricated utilizing Si substrates and P3HT. SEM, TEM were used tocharacterize the device structure; J-V and EQE were used to evaluate the deviceperformance; the fitting of dark current was utilized to investigated the effect of deviceperformance influenced by the morphology and passivation of Si substrates surfaces.The results indicated that the desity of SiNWs should be suitable so as to formcontinuous organic films.4. Fabrication of hybrid Schottky heterojunction photovoltaic solar cells based onSiNWswith different morphology and PEDOT:PSS. The device structure wascharacterized by SEM, UV-Vis etc.; the device performance was characterized by J-Vand EQE test; the interface quality was investigated by fitting dark current and transientphotovoltage decay test. The results indicated that the density and length of SiNWsshould be suitbale to balance the light trpping and surface trap states.5. Passivation of the Si surfaces to suppress the charge recombination. The alkygroup coverage ratio was exactly demonstrated by grazing angle attenuated totalreflectance Fourier-transform infrared spectroscopy (GATR-FTIR) and XPS. HybridSchottky photovoltaic devices based on PEDOT:PSS and different coverage ratiopassivated SiNWs by varying organic monolayer were fabricated. The device structurewas characterized by SEM, TEM and UV-Vis. The device performance wascharacterized by J-V and EQE test; the interface engineering was investigated by fittingdark current and transient photovoltage (photocurrent) decay test. The results indicatedthat the mixed organic monolayer could passivate SiNWs surface completely andenhance the device performance efficiently.