CAJ | 학술논문

衬底温度保持恒定,在 Se 气氛下按照一定的元素配比顺序蒸发 Ga, In, Cu 制备厚度约为0.7μm 的Cu(In0.7Ga0.3)Se2(CIGS)薄膜.利用X 射线衍射仪分析薄膜的晶体结构及物相组成,扫描电子显微镜表征薄膜形貌及结晶质量,二次离子质谱仪测试薄膜内部元素分布,拉曼散射谱分析薄膜表面构成,带积分球附件的分光光度计测量薄膜光学性能.研究发现在Ga-In-Se预制层内, In主要通过晶界扩散引起Ga/(Ga+In)分布均匀化.衬底温度高于450?C时,薄膜呈现单一的Cu(In0.7Ga0.3)Se2相;低于400?C,薄膜存在严重的Ga的两相分离现象,且高含Ga相主要存在于薄膜的上下表面;低于300?C,薄膜结晶质量进一步恶化.薄膜表层的高含Ga相Cu(In0.5Ga0.5)Se2以小晶粒形式均匀分布于薄膜表面,增加了薄膜的粗糙度,在电池内形成陷光结构,提高了超薄电池对光的吸收.加上带隙值较小的低含Ga相的存在,使电池短路电流密度得到较大改善.衬底温度在550?C—350?C变化时,短路电流密度JSC是影响超薄电池转换效率的主要因素;而衬底温度Tsub低于300?C时,开路电压VOC和填充因子FF降低已成为电池性能减退的主要原因. Tsub为350?C时制备的0.7μm左右的超薄CIGS电池转换效率达到了10.3%.
츤저온도보지항정,재 Se 기분하안조일정적원소배비순서증발 Ga, In, Cu 제비후도약위0.7μm 적Cu(In0.7Ga0.3)Se2(CIGS)박막.이용X 사선연사의분석박막적정체결구급물상조성,소묘전자현미경표정박막형모급결정질량,이차리자질보의측시박막내부원소분포,랍만산사보분석박막표면구성,대적분구부건적분광광도계측량박막광학성능.연구발현재Ga-In-Se예제층내, In주요통과정계확산인기Ga/(Ga+In)분포균균화.츤저온도고우450?C시,박막정현단일적Cu(In0.7Ga0.3)Se2상;저우400?C,박막존재엄중적Ga적량상분리현상,차고함Ga상주요존재우박막적상하표면;저우300?C,박막결정질량진일보악화.박막표층적고함Ga상Cu(In0.5Ga0.5)Se2이소정립형식균균분포우박막표면,증가료박막적조조도,재전지내형성함광결구,제고료초박전지대광적흡수.가상대극치교소적저함Ga상적존재,사전지단로전류밀도득도교대개선.츤저온도재550?C—350?C변화시,단로전류밀도JSC시영향초박전지전환효솔적주요인소;이츤저온도Tsub저우300?C시,개로전압VOC화전충인자FF강저이성위전지성능감퇴적주요원인. Tsub위350?C시제비적0.7μm좌우적초박CIGS전지전환효솔체도료10.3%.
In the presence of Se, Cu(In0.7Ga0.3)Se2 (CIGS) thin films are prepared by the sequential evaporation of Ga, In, Cu at a constant substrate temperature between 250 ?C and 550 ?C on the Mo/soda lime glass substrates. The thickness values of films are about 0.7 μm. The structural and phase properties of CIGS films are studied by an X-ray diffractometer, the morphology and crystalline quality are characterized by a scanning electron microscope, the depth profiles of elements are measured by a secondary ion mass spectroscopy, the surface compositions are analyzed by a Raman spectrometer, and the optical properties of CIGS films are measured by a spectrophotometer with an integrating sphere. It is found that the films prepared at substrate temperature above 450 ?C each exhibite a single Cu(In0.7Ga0.3)Se2 phase, and the homogenization of Ga/(Ga+In) distribution in the Ga-In-Se precursor is achieved by the diffusion of In atoms through grain boundaries. As the substrate temperature is less than 400 ?C, a serious Ga phase separation is observed and the high content of Ga phase mainly exists at the top and bottom of CIGS films. Below 300 ?C, a serious deterioration of crystalline quality is found, and Ga atoms cannot effectively enter into the CIS lattice position to form CIGS. The films prepared at the substrate temperature less than 400 ?C are covered with lots of Cu(In0.5Ga0.5)Se2 small grains, which results in the enhancement of the surface roughness and the formation of a light trapping structure at the interface of Cd/CIGS. Thus, the light absorption of solar cell is improved. In addition, the smaller gap value of the low Ga content phase also facilitats the light absorption, then the short-circuit current density of thinned solar cell is greatly improved. The analysis shows that the short-circuit current density is the main factor affecting the conversion efficiency of thinned solar cell prepared between 550 ?C–350 ?C. However, when the substrate temperature is below 350 ?C, the reduction of VOC and FF has become the main reason for the deterioration of solar cell. In conclusion, the efficiency of solar cell with 0.7 μm CIGS absorber prepared at substrate temperature of 350 ?C reaches 10.3%due to the improvement of short-circuit current density.