Thin Film Solar Cells based on CIS Research for production of cheap and efficient solar modules Marika Edoff, Ångström Solar Center, Uppsala University, Sweden Email: Marika.Edoff@angstrom.uu.se 1
partners 7 partners from 3 EC countries and Switzerland Uppsala University Uppsala, Sweden Ecole Nationale de Chimie de Paris Paris, France Zentrum für Sonnenenergie und Wasserstoff- Forschung Stuttgart, Germany Electricité de France Paris, France University of Stuttgart Stuttgart, Germany Coordinator Eidgenössische Technische Hochschule Zürich, Switzerland Würth Solar Marbach, Germany 2
Sun as energy source 3
Visions for the future A solar module roof on all houses 50 m 2 facing south (south-east to south-west), tilted Produces 5000-6000 kwh/year in Northern Europe and 7000-8000 kwh/year in sunniest parts of Europe (12.5 % efficiency) Enough for household electricity of one family A solar module factory in every larger city A large factory (100 MW p* ) produces 800000 m 2 of solar modules/year (at 12.5 % efficiency) Provides solar modules for 10000 houses/year Employs about 500 people *Wp is a standardized measure of solar module performance, A solar module of 100 W p produces 100 W in full sunlight 4
From light to electricity in one step Solar cells only work when illuminated Front contact Active layer Back contact The sunlight is absorbed in the active layer - + A voltage is created between the front contact and the back contact 5
CIS solar modules Examples of solar modules in northern Europe Monocrystalline Si Source: IEA-PVPS Sol-300 project, Denmark Photo, Würth Solar Friedenskirche, Tübingen, Germany 160 m 2 CIS modules produce 11 000 kwh/year Hammarby Sjöstad, Stockholm, Sweden Polycrystalline Si Source: IEA-PVPS 6
Different kinds of solar modules CIS solar modules (PROCIS technology): Module efficiency in production 11-12 % Thin films: 20-30 grams of solar cell material for 1 m 2 of solar cell area It takes 150 kwh to make 1 m 2 of thin film solar module Fully automized production methods Crystalline silicon solar modules Module efficiency in production 13-15 % 1 kg of silicon for 1 m 2 of solar cell area It takes 550 kwh to make 1 m 2 of silicon based solar module Handling of wafers needed 7
What is a CIS solar cell? Copper, Indium and Selenium, the elements of the heart of the solar cell, have given it its name: CIS The thickness of a hair is about 0.1 mm 1 2 The thickness of all the active layers in the CIS solar cell is 0.004 mm 3 4 5 1. Front contact layer 2. Buffer layer 3. CIS layer 4. Back contact layer 5. Glass substrate 8
Easy to make CIS solar modules The CIS technology A solar cell gives about 0.5 volt Many cells connected together make a solar module CIS solar cells are interconnected during the fabrication of the thin layers - no handling of individual cells as in the conventional techniques Encapsulation needed for both Si and CIS to protect the solar cells Crystalline Si module CIS module 9
The main objective of To make the CIS solar modules cheaper by: Make the CIS layer even thinner More solar modules in less time Less need for expensive and scarce materials Improve productivity Reduce production failures, e.g. glass breakage and glass deformation Completely Cd-free solar modules Cadmium is a heavy metal and should be avoided in products as well as in the working environment 10
Sheet of glass Standard process for CIS Production of solar modules 4 layers, 4 fabrication processes Solar modules move through the processes on a conveyor belt All processes put together as links in a chain Sheets of glass go through the chain of processes Slowest link in the chain limits production speed Back contact CIS Buffer Front contact Pile-up of unfinished modules 11
Faster CIS production process Bottleneck in production eliminated Betteruse of otherlinks in the chain Cheaper modules PROCIS Production of solar modules Back contact CIS Buffer Front contact 12
EC project PROCIS results Research lab: solar cells with 1/3 of CIS thickness Industrial partner of PROCIS project: 20% higher solar module production World record for any thin film solar module (16.6 % efficiency) Completely Cd-free module with 12.9 % efficiency The Cd-free 12.9 % solar module 13