Huawei has also downgraded its forecast for total smartphone shipments in the second half of 2019.
Apple says it aims to have suppliers sign power-purchase agreements with new renewable energy projects.
Several Apple component makers warned of weaker than expected results, leading some market watchers to call the peak for iPhones.
TSMC has said it maintained its previous forecast of high single-digit revenue growth for 2018.
Apple shares fall after analysts predict softer smartphone sales from TSMC's revenue target hinting at lower iPhone demand
Apple’s shares were last down 2.5 percent and were the biggest drag on the tech-heavy Nasdaq index.