Six more countries have signed agreements to join the International Solar Alliance (ISA).
Five African nations – Djibouti, Cote d’Ivoire, Somalia, Ghana and Comros – join other nations who signed the pact in November last year.
A tiny island, Nauru, which has a population of just above 10,000, also submitted its instrument of ratification.
The ISA was launched at the UN Climate Change Conference in Paris in 2015 by Indian Prime Minister Narendra Modi and French President Francois Hollande.
The alliance aims to make solar power affordable and reliable across all countries and mobilise $1 trillion (£0.7tn) of investment by 2030.
The total support from the Indian Government for the project, including the cost of the land, will be around Rs 400 crore ($47.9m).
Last year the World Bank signed an agreement with an alliance of 121 countries led by India to collaborate on increasing solar energy use across the globe.